Today, some vehicles are provided with collision mitigation systems or collision avoidance systems that includes a radar and vision sensor arrangement. These systems are arranged to detect moving objects such as vehicles and pedestrians as well as stationary objects such as roadway structures ahead in the traveling path of the vehicle.
As a result, such a system may provide a safety action in the form of for example a warning and/or automatic braking when it is determined that the possibility of a collision between the vehicle and a detected object has exceeded a threshold.
U.S. Pat. No. 6,035,053 discloses a moving object recognizing system arranged for detecting objects, where the transverse velocity of the object is taken into account in order to decrease the number of alarms.
For a typical previously known collision mitigation system, for example as described in U.S. Pat. No. 6,035,053, a pedestrian who is going to cross a vehicle's traveling path ahead of the vehicle may rush out into the road, which requires detection well in advance. For a detected pedestrian, being outside the vehicle's traveling path, it may be decided whether it is likely that the pedestrian will cross the traveling path in such a way that there is a possibility of collision. Such a decision may be made before the pedestrian appears in the vehicle's traveling path.
However, this may cause unnecessary safety actions, for example in form of warnings and braking, which in turn themselves may cause accidents, since it is difficult to determine whether a pedestrian approaching the vehicle's traveling path in fact will enter the vehicle's traveling path such that a collision will occur, or if the pedestrian will stop before a collision occurs.
Early decisions regarding a safety action give high safety but may result in many unnecessary safety actions. Late decisions give less unnecessary safety actions, but offer limited time to brake and warn.
Furthermore, a system which has been factory tuned to operate well in areas with few pedestrians, may cause a high number of activations in areas with a lot of pedestrians. There are thus different needs in different situations.
A collision mitigation system with many unnecessary safety actions will at least constitute a disturbance, and may also be a potential danger.
Also, it may be desired to have a certain trigger rate regarding one or several safety actions in order to have a collision mitigation system which provides confirmation of its existence and functionality.
It is therefore an object of the present invention to provide a collision mitigation system where the number of activations is adjusted in order to acquire a more reliable and usable collision mitigation system of this type, while maintaining a desired trigger rate. In this context, initially a trigger rate is preferably factory set.